Conventionally, a pressure switch, a pressure sensor or a valve that is connected to a pipe of a refrigerant circuit is known, and examples thereof are disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 2005-205231 (Patent Literature 1; will be mentioned below). For example, such conventional pressure switch has a lid member 1 made from stainless, and a coupling (connector) 2 made from brass. The lid member 1 is diffusion-joined with the coupling 2 by projection welding (resistance welding). The coupling 2 is then connected to the pipe of the refrigerant circuit, and a fluid is introduced into the lid member 1 through an inside hole 22 at the center of the coupling 2 and a through hole 12 of the lid member 1.
This conventional pressure switch also has an outer projection 25 for projection welding and an inner projection 26, which is shorter than the outer projection 25, such that spatter, which is generated upon the projection welding, is prevented from flowing into the refrigerant circuit.
Specifically, the outer projection 25 is melted by the projection welding, and the inner projection 26 is deformed by a pressure-joining force, which clamps and presses the lid member 1 and the coupling 2, such that the space for receiving the spatter is sealed.